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Covering
the Ozone Hole As the annual stratospheric ozone hole over the Antarctic reaches its peak in mid-late September, news coverage inevitably results. While terrorist attacks may sweep it off the front pages this year, it is a story that will recur year after year. On Oct. 16-19, 2001, the parties to the Montreal Protocol were scheduled to meet in Colombo, Sri Lanka. Why Cover Stratospheric Ozone Depletion? The stratospheric ozone layer is critical to life on Earth. Before Earth's oxygen atmosphere formed, life was limited to the sea, because the sun's ultraviolet radiation would have been lethal to any creature living on land. The ozone layer, which is formed as sunlight breaks down oxygen molecules, filters out the most harmful kinds of incoming solar ultraviolet. Chemicals put into the atmosphere by humans have eroded this protective layer, increasing certain dangers to people and other forms of life. Perhaps the chief threat to human health from increased ultraviolet exposure is skin cancer. The causal connection between ultraviolet exposure and skin cancer is well-established scientifically. There are more than a million new cases of skin cancer yearly in the United States a lone, thousands of them fatal. One in five Americans will develop skin cancer during their lifetime. Roughly one American dies every hour from skin cancer. Story Ideas 1. How big is this year's Antarctic stratospheric ozone hole -- which usually peaks in mid-late September? How does it compare to previous years? What is the overall trend over recent decades? 2. Is there a stratospheric ozone hole over the Arctic this year? How big is it and how does it compare to previous years? 3. How would people in your latitude be affected by stratospheric ozone depletion? What are the measured stratospheric ozone levels and the trends in them? What are the measured UV levels and the trends in them? 4. Can the ozone issue be ignored now that the Montreal Protocol and several additions to it have been agreed on and signed? -- or is the problem an ongoing one? Why? 5. Since some of the major problem CFCs have been phased out under the Montreal Protocol, a black market in CFCs has emerged. What uses do businesses and industries in your area still make of CFCs? Where do they come from and where are they disposed of? Has EPA prosecuted anyone in your area for illegal traffic in CFCs lately? How do auto repair shops in your area handle CFCs and air conditioning system refrigerants? 6. What will the impact of the methyl bromide phase-out be in your area? Will it affect agriculture and food industries in your area? 7. What can individual consumers do to protect the ozone layer? What are the best practices for a consumer to follow in getting his or her auto air conditioning system serviced? 8. If there are semiconductor industries in your area, what are their practices with regard to halocarbon use and recovery? Background and Context Oxygen, the life-giving element that comprises about 20 percent of Earth's atmosphere, normally occurs in molecules consisting of two atoms of elemental oxygen chemically bound to each other. Ozone, a molecule made up of three oxygen atoms, is rarer and more unstable. At ground level, it is a pollutant which can irritate and damage people's lungs, but in the stratosphere, it protects us from harmful ultraviolet rays. Incoming ultraviolet rays from the sun create ozone when they break apart normal oxygen molecules, and some of the atoms recombine to form ozone. Ozone in the stratosphere is constantly being created and destroyed in a dynamic and complex chain of chemical reactions. Stratospheric ozone is hardly a static or permanent thing, and its abundance at any given place and time is the result of an ever-changing balance of forces. In 1974, two University of California chemists, F. Sherwood Rowland and Mario Molina, published a paper predicting that the buildup of chlorofluorocarbons (CFCs) in the stratosphere could radically alter the balance of stratospheric chemistry, because they functioned as a long-lived catalyst promoting destruction of ozone. In 1977, the federal government began banning nonessential uses of CFCs in aerosol spray products. The issue was largely ignored until about 1985. In that year, many nations signed the Vienna Convention, which covered research and monitoring of stratospheric ozone, but said nothing about controlling CFCs. In the same year, a team of British scientists led by Dr. Joe Farman published data gathered the year before, revealing an astonishing discovery. They found a 40 percent ozone loss over Antarctica during the southern hemisphere spring - the "ozone hole." By 1987, nations had signed the Montreal Protocol, which called for CFC reductions of 50 percent by 1999. The Montreal treaty was further amended in London in 1990, Copenhagen in 1992, Vienna in 1995, Montreal in 1997, and Beijing in 1999 -- adding new ozone-depleting substances to be phased out and tightening deadlines. The CFCs are really a whole family of chemical compounds, and part of a still-large chemical clan called the halocarbons, many of which can destroy ozone. Each compound has different uses, and each has different potential for destroying ozone. Since manufacturers decided voluntarily to stop making them, the most harmful and ubiquitous compounds, like CFC-11 and CFC-12, have largely been removed from legitimate commerce, at least in new uses. But this hardly means the problem is "solved." For one thing, stability and non-reactivity were essentially the qualities that made these chemicals so attractive for various industrial uses in the first place. Many do not break down easily and persist for a long time -- decades or centuries -- once they get into the atmosphere. Their ozone-depleting effect will persist as a result, and we can expect annual ozone holes over the Antarctic to continue for decades. For another thing, the CFC substitutes can create problems also. Some of the substitutes, such as the hydrochloro-fluorocarbons (HCFCs), have far less ozone-depleting effect, but still do deplete ozone. Others, such as the family known as hydrofluoro-carbons (HFCs), have no ozone-depleting effect, but do add to global climate warming. The Montreal Protocol and the treaties extending it now go well beyond the CFCs which were the original concern. Other ozone-depleting chemicals it now addresses include halons (used in fire extinguishers), and methyl chloroform (an industrial solvent). One of the most controversial is methyl bromide, which is used as a pesticide in agriculture and food processing. Phase-out of methyl bromide has only just begun. The World Meteorological Organization and other scientific groups concluded, in their 1998 scientific assessment, that "The total combined abundance of ozone-depleting compounds in the lower atmosphere peaked in about 1994 and is now slowly declining. Total chlorine is declining, but total bromine is still increasing." Bromine atoms have a stronger ozone-depleting effect than chlorine atoms. Even if all provisions of the Montreal Protocol were fully enforced, the 1998 WMO assessment estimated that "the maximum ozone depletion is estimated to lie within the current decade or the next two decades," with ultimate recovery only decades beyond that. Sources and Players U.S. Environmental Protection Agency
National Oceanic & Atmospheric Administration (NOAA)
National Aeronautics and Space Administration (NASA)
UNEP "Ozone Secretariat"
World Meteorological Organization
Alliance for Responsible Atmospheric Policy
Reprinted with permission. Published in Environment Writer newsletter, September 2001, by the National Safety Council's Environmental Health Center.
March 2003 |
